1. Field of the Invention
The present invention relates to a resist composition for intricate pattern working required for production of photomasks and electronic devices, and to a pattern forming process and photomask production process employing the resist.
Electronic devices are exhibiting ever higher performance with greater miniaturization of circuit patterns. Miniature patterns are usually formed using photosensitive resin compositions known as photoresists. Specifically, a photoresist film is formed on a substrate and, after exposing a circuit pattern by radiation, it is developed to form the resist pattern, the pattern being then transferred to the target substrate by a method such as etching to form a circuit pattern on the substrate.
2. Description of the Related Art
Formation of high-precision circuit patterns requires a well-balanced resolution of the resist patterns after development. However, as circuit patterns become more miniaturized, it has become difficult to achieve such well-balanced resolution of resist patterns. For example, with copolymers of chloromethylstyrene and chiorostyrene in electron beam radiation negative-type resists used for production of photomasks, greater miniaturization of patterns results in problems such as roughness of the pattern edges due to the effects of forward scattering and back scattering of the electron beam in the resist film, and there is considerable production of substantial residues in the spaces.
It is therefore an object of the present invention to overcome such problems of the prior art by providing resist compositions and a pattern forming process employing them, whereby high resolution resist patterns can be obtained.
As a result of diligent research directed toward solving these problems, the present inventors have completed the present invention upon the finding that the resolution of resists can be improved by adding specific additives to the resists.
Specifically, the invention provides a resist composition comprising, in a resist, an additive which has a melting point of 160xc2x0 C. or above, contains no aromatic ring, has a molecular size of no greater than 50 xc3x85 and is soluble in the developing solution for the resist, at 1-50 parts by weight with respect to 100 parts by solid weight of the resist.
According to the invention there is further provided a process for forming patterns comprising the steps of forming a film of the aforementioned resist composition on a target substrate, irradiating it with radiation, baking it if necessary, and then developing it. This pattern forming process can be advantageously applied to production of semiconductor apparatuses.
According to the invention there is still further provided a process for producing photomasks comprising the steps of forming a film of the aforementioned resist composition on a mask substrate, irradiating it with radiation, baking it if necessary, and then developing it and using the resulting resist pattern for etching of the mask substrate. Here, the term xe2x80x9cphotomaskxe2x80x9d is used in a wide sense to include reticle masks.